Proposed uses and advantages for high current, high transition temperature superconductors have not been realized, given that commercially usable superconductor materials in bulk form (including thick films) are still generally unavailable. Superconductor refers here and in the following description to the class of ceramic superconductors containing copper oxide or other oxides and having superconductivity transition temperatures (T(c)) generally above the liquid nitrogen boiling temperature (77K). Critical currents J(c) greater than 10.sup.4 A/cm.sup.2 at magnetic fields of 10T are considered necessary for practical, current carrying applications. A small amount of superconductor material with such critical current carrying capability has been fabricated but no proven method exists for repeatably or controllably fabricating a bulk superconductor material with such high J(c) at operating temperatures of 77K. Currently, superconductors with high values of J(c) can be produced only in epitaxial thin films and monocrystals. Both are unsuitable and impractical for most commercial applications. Thick superconductor films of high J(c) may be produced by a melt-textured growth process. However, these films cannot be made a practical thickness without loss of grain orientation and accompanying drop of J(c).
It has been previously shown that low values of J(c) result from the disorientation of the crystal lattice structure. The crystal lattice of all presently known high-T(c) superconductors is considerably anisotropic, and includes a high-current carrying (ab) plane. These are also the planes of high conductivity in a normal state, whereas the conductivity in the crystal c-direction, normal to (ab) plane, is several orders of magnitude lower than the conductivity along the (ab) plane direction.
The use of superconductor material (such as Y-Ba-Cu-O-compound) in which crystalline grains are aligned in a strong magnetic field along the c-axis results in some increase of J(c). See U.S. Pat. No. 4,288,398 and U.S. Pat. No. 4,842,704. Recently, it has been shown that the use of multi-axial alignment of superconductor crystals utilizing two anisotropic properties of the crystals that are perpendicular to one another results in a considerable increase in critical current carrying capability. See U.S. application Ser. No. 07/490,752. This multi-axial alignment is accomplished by using two forces of different origin. The first alignment force to which the crystals are reactive is provided to align the crystals along the c-axis to orient the crystals coplanar in the (ab) plane with one another. The crystals are also subjected to a magnetic field to provide the second alignment force. This magnetic force aligns a magnetic moment of the crystals along an axis that lies within the conducting plane and which is generally transverse to the c-axis. This magnetic moment, however, is primarily the result of adding a rare earth element to the crystalline material and thus, not all superconductor material contains or is capable of receiving such an added element. Most importantly, every superconductor material to which has been added a rare earth element may align along a different axis based upon the crystalline material itself and the added rare earth element.
It has been further suggested to align the crystals along a first axis by such alignment forces as gravity, centrifugal force, deforming or shear pressure, or an electric field Accordingly, a superconducting material must be provided having either a shape anisotropy to produce the alignment along the first axis by means of gravitational or centrifugal pressing, which mechanically urges the crystals into intended alignment; having deformation anisotropy to provide the alignment by use of pressure, rolling or other shear deformation force; and having an electrical anisotropy to provide the alignment by an applied electric field. The above features are not inherent features of oxide superconductors so these conditions restrict the spectrum of materials available for axial alignment.